Electric motor having an integrated cooling system and methods of cooling an electric motor

ABSTRACT

The present disclosure pertains to electric machines such as electric propulsion systems for aircraft that integrated cooling systems, and methods of cooling such an electric machine. Exemplary electric machines include an electric motor that has a stator, a rotor, and a drive shaft operably coupled to the rotor. Exemplary electric machines further include a motor cooling conduit that defines a pathway for conveying a cooling fluid through or around at least a portion of the electric motor, a casing assembly that circumferentially surrounds at least a portion of the electric motor, a casing assembly conduit integrally formed within at least a portion of the casing assembly which defines a pathway for conveying the cooling fluid through the at least a portion of the casing assembly, and a pump or compressor operably coupled to the drive shaft and configured to circulate the cooling fluid through the motor cooling conduit and the casing assembly conduit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 16/006,094 filed Jun. 12, 2016, titled “ELECTRIC MOTOR HAVING ANINTEGRATED COOLING SYSTEM AND METHODS OF COOLING AN ELECTRIC MOTOR,”herein incorporated by reference.

FIELD

The present disclosure relates to electric machines with integratedcooling systems and methods of cooling an electric machine, and electricpropulsion systems for aircraft that utilize such systems and methods.

BACKGROUND

Electric motors and similarly electric propulsion systems for aircrafttypically require a cooling system to cool the electric motor orpropulsion system. Such as cooling system typically includes a heatexchanger and a pump coupled together with various pipes, hoses,fittings, and the like to circulate fluid between the motor and the heatexchanger. These components add weight, which reduces the power densityof the motor or propulsion system. Additionally, these components andtheir associated pipes, hoses, fittings, and the like increase the stepsrequired to install or uninstall an electric motor or propulsion systemon an aircraft. Accordingly, there exists a need for electric motors andelectric propulsion systems for aircraft with improved cooling systemsand improved methods of cooling an electric motor.

BRIEF DESCRIPTION

Aspects and advantages will be set forth in part in the followingdescription, or may be obvious from the description, or may be learnedthrough practicing the presently disclosed subject matter.

In one aspect, the present disclosure embraces electric machines thathave an integrated cooling system. An exemplary electric machineincludes an electric motor that has a stator, a rotor, and a drive shaftoperably coupled to the rotor. An exemplary electric machine furtherincludes a motor cooling conduit, a casing assembly that includes acasing assembly conduit integrally formed within at least a portion ofthe casing assembly, and a pump or compressor operably coupled to thedrive shaft and configured to circulate the cooling fluid through themotor cooling conduit and the casing assembly conduit. The motor coolingconduit defines a pathway for conveying a cooling fluid through oraround at least a portion of the electric motor, and the motor coolingconduit has a thermally conductive relationship with the at least aportion of the electric motor. The casing assembly circumferentiallysurrounds at least a portion of the electric motor. The casing assemblyconduit defines a pathway for conveying the cooling fluid through the atleast a portion of the casing assembly, and the casing assembly conduithas a thermally conductive relationship with an external surface of thecasing assembly.

In another aspect, the present disclosure embraces an electricpropulsion system for an aircraft. An exemplary electric propulsionsystem includes an electric motor that has a stator, a rotor, and adrive shaft operably coupled to the rotor. Exemplary electric propulsionsystems include a motor cooling conduit that defines a pathway forconveying a cooling fluid through or around at least a portion of theelectric motor, and the motor cooling conduit has a thermally conductiverelationship with the at least a portion of the electric motor. Anexemplary electric propulsion system further includes a fan or propelleroperably coupled to the drive shaft. Further, the exemplary electricpropulsion system includes a casing assembly that circumferentiallysurrounds at least a portion of the electric motor. The casing assemblyincludes a motor casing, a nacelle, a plurality of support memberscircumferentially supporting the nacelle about the motor casing, and acasing assembly conduit integrally formed within at least a portion ofthe casing assembly. The casing assembly conduit defines a pathway forconveying the cooling fluid through the at least a portion of the casingassembly, and the casing assembly conduit has a thermally conductiverelationship with an external surface of the casing assembly. Theexemplary electric propulsion system further includes a pump orcompressor operably coupled to the drive shaft, with the pump orcompressor being operably configured to circulate cooling fluid throughthe motor cooling conduit and the casing assembly conduit.

In yet another aspect, the present disclosure embraces methods ofcooling an electric machine, such as an electric machine used forpropulsion of an aircraft. An exemplary method includes circulating acooling fluid through a motor cooling conduit that defines a pathway forconveying a cooling fluid through or around at least a portion of anelectric motor that has a stator and a rotor. The motor cooling conduithas a thermally conductive relationship with the at least a portion ofan electric motor, and the exemplary method includes transferring heatfrom the electric motor to the cooling fluid circulating through themotor cooling conduit by the thermally conductive relationship with theat least a portion of the electric motor. The exemplary method furtherincludes circulating the cooling fluid through a casing assembly conduitintegrally formed within at least a portion of a casing assembly. Thecasing assembly conduit defines a pathway for conveying the coolingfluid through the at least a portion of the casing assembly, and thecasing assembly circumferentially surrounds at least a portion of theelectric motor. The casing assembly conduit has a thermally conductiverelationship with an external surface of the casing assembly, and theexemplary method includes transferring heat from the cooling fluidcirculating through the casing assembly conduit to airflow passing overthe external surface of the casing assembly by the thermally conductiverelationship with the external surface of the casing assembly. Thecooling fluid is circulated through the motor cooling conduit and thecasing assembly conduit at least in part by a pump or a compressoroperably coupled to a drive shaft, with the drive shaft also operablycoupled to the rotor of the electric motor.

These and other features, aspects and advantages will become betterunderstood with reference to the following description and appendedclaims. The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments and, together with the description, serve to explain certainprinciples of the presently disclosed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure, including the best mode thereof,directed to one of ordinary skill in the art, is set forth in thespecification, which makes reference to the appended Figures, in which:

FIG. 1 schematically shows an exemplary electric propulsion system foran aircraft;

FIGS. 2A-2C schematically show respective alternative embodiments of anelectric motor with an integrated cooling system that utilizessingle-phase cooling;

FIGS. 3A-3C schematically show respective alternative embodiments of anelectric motor with an integrated cooling system that utilizes two-phasecooling;

FIGS. 4A and 4B schematically show aspects of a casing assembly with acasing assembly conduit integrally formed therein; and

FIG. 5 shows a flowchart of a method of cooling an electric motor usedfor propulsion of an aircraft.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to exemplary embodiments of thepresently disclosed subject matter, one or more examples of which areillustrated in the drawings. Each example is provided by way ofexplanation and should not be interpreted as limiting the presentdisclosure. In fact, it will be apparent to those skilled in the artthat various modifications and variations can be made in the presentdisclosure without departing from the scope or spirit of the presentdisclosure. For instance, features illustrated or described as part ofone embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present disclosurecovers such modifications and variations as come within the scope of theappended claims and their equivalents.

The present disclosure generally pertains to electric motors andelectric propulsion systems that have integrated cooling systems, andmethods of cooling an electric motor or propulsion system. As an examplethe presently disclosed electric motors and electric propulsion systemsmay be employed in an aircraft, such as for propulsion of the aircraft,including in commercial, military, or civilian aircraft, as well asunmanned aircraft such as unmanned aerial vehicles, electric rotorcraft,drones, and the like.

The presently disclosed electric motors and electric propulsion systemsinclude a stator, a rotor, a drive shaft operably coupled to the rotor,and a pump or compressor operably coupled to the drive shaft, andconfigured to circulate cooling fluid through a motor cooling conduitand a casing assembly conduit. The motor cooling conduit defines apathway for conveying a cooling fluid through or around at least aportion of the electric motor or electric propulsion system. The casingassembly conduit defines a pathway for conveying the cooling fluidthrough at least a portion of a casing assembly that circumferentiallysurrounds at least a portion of the electric motor or propulsion system.An electric propulsion system for an aircraft may include a presentlydisclosed electric motor with a fan or propeller operably coupled to thedrive shaft.

The integrated cooling system provides electric motors and propulsionsystems that have a higher power density, are more efficient, and easierto install and uninstall. In some embodiments, the integrated coolingsystem may address certain thermal management needs of the electricmotor or propulsion system, which in some embodiments may reduce oreliminate certain needs for auxiliary components, such as externalpumps, external heat exchangers as well as associated pipes, hoses, andfittings, and the like. This may allow for electric motors that can beinstalled, for example, in an electric propulsion system of an aircraft,without requiring certain service connections apart from powerconnections for the electric motor and associated electronics fordiagnostics and controls. In some embodiments the presently disclosedelectric motors and propulsion systems with integrated cooling systemsmay allow for more compact, lighter-weight components, which furtherimproves power density and operating efficiency.

Various embodiments of the present disclosure will now be described ingreater detail. Referring to FIG. 1 , an exemplary electric machineand/or electric propulsion system 100 for an aircraft is shown. In theexample embodiment, the electric propulsion system 100 is ahybrid-electric turbine engine. In general, the electric propulsionsystem 100 includes an electric motor 102 and a fan section 104 drivenby the electric motor 102. In some embodiments, a core turbine engine(not shown) may be disposed downstream from the fan section 104. Theelectric motor 102 includes a stator 106 and a rotor 108. The rotor 108is operably coupled to a driveshaft 110.

For the embodiment depicted, the fan section 104 includes a fan 112(e.g., a variable pitch fan) having a plurality of fan blades 114operably coupled to the drive shaft 110 in a spaced apart manner androtatable about longitudinal axis A by the drive shaft 110.Alternatively, or in addition, the electric propulsions system mayinclude a propeller or other rotatable airfoil assembly. The fan orpropeller 112 may be operably coupled to the drive shaft 110 directly oracross a gear box 116 that includes a plurality of gears for adjustingthe rotational speed of the fan or propeller 112 relative to the driveshaft 110 to a more efficient rotational speed.

A casing assembly 118 includes an annual casing that circumferentiallysurrounds at least a portion of the electric propulsion system 100. Thecasing assembly 118 shown in FIG. 1 includes a motor casing 120 (e.g. acowling, a housing, etc.), a fan casing or nacelle 122, and a pluralityof circumferentially spaced support members (e.g., fan outlet guidevanes and/or struts) 124. The motor casing 120 circumferentiallysurrounds at least a portion of the fan 112, the electric motor 102,and/or the core turbine engine. The fan casing or nacelle 122circumferentially surrounds at least a portion of the motor casing 120,the fan section 104, the electric motor 102, and/or the core turbineengine. The nacelle 122 has an outer surface 126 and an inner surface128. A space between the inner surface 128 of the nacelle 122 and themotor casing 120 defines a bypass airflow passage 130. The supportmembers 124 span the bypass airflow passage 130, from the motor casing120 to the inner surface 128 of the nacelle 122. The support members 124may circumferentially support the fan casing or nacelle 122 about themotor casing 120, and may optionally include an aerodynamicconfiguration (e.g., in the case of a fan outlet guide vane). In oneembodiment, the support members may include both fan outlet guide vanes125 and struts 127. In another embodiment, the support members mayinclude fan outlet guide vanes 125 that provide sufficient support suchthat the struts 127 may be omitted. When the struts 127 are included,the struts 127 may or may not include an aerodynamic configuration. Anelectric propulsion system 100 may include any number of support members124, such as from 10 to 50 support members, or from 20 to 40 supportmembers. In one embodiment, an electric propulsion system 100 mayinclude between 20 to 40 fan outlet guide vanes 125 and between 2 to 6struts 127.

During operation of the electric propulsion system 100, a volume of air132 enters an inlet 134, while an adjacent volume of air 136 passesalong the outer surface 126 of the nacelle 122. As the volume of air 132passes across the fan blades 114, a first portion of air 132 asindicated by arrows 138 is directed or routed into the bypass airflowpassage 130, and a second portion of air 132 as indicated by arrow 140is directed or routed into a core air flowpath of the core turbineengine (not shown). The ratio between the first portion of air 138 andthe second portion of air 140 is commonly known as a bypass ratio.

The second portion of air 140 is routed through various stages of thecore turbine engine, rotating turbine rotor blades which supportrotation of the drive shaft 110. The second portion of air 140 issubsequently routed through a jet exhaust nozzle section 142 of coreturbine engine to provide propulsive thrust. Simultaneously, thepressure of the first portion of air 138 is substantially increased asthe first portion of air 132 is routed through the bypass airflowpassage 130 before being exhausted from a fan nozzle exhaust section144, also providing propulsive thrust.

While the electric propulsion system 100 described above provides oneexemplary embodiment, it should be appreciated that the exemplaryembodiment is described by way of example only, and that in otherexemplary embodiments, the electric propulsion system 100 may have othersuitable configurations. It should also be appreciated, that in stillother exemplary embodiments, aspects of the present disclosure may beincorporated into other suitable electric propulsion systems for anaircraft. For example, in other exemplary embodiments, aspects of thepresent disclosure may be incorporated into an electric turboprop engineor other electric propulsion system for an aircraft. Additionally,aspects of the present disclosure may be incorporated into manned orunmanned aircraft.

Exemplary electric motors or electric propulsion systems include anintegrated cooling system, which will now be described in further detailwith reference to FIGS. 2A-2C, 3A-3C, and 4A and 4B. The integratedcooling system 200, 300 may utilize single-phase cooling (FIGS. 2A-2C)or two-phase cooling (FIGS. 3A-3C).

As shown in FIGS. 2A-2C, an electric motor or electric propulsion systemwith an integrated cooling system 200 includes a pump 202 operablyconfigured to circulate cooling fluid through a fluid pathway 204 thatincludes a motor cooling conduit 206 configured to cool an electricmotor 102, and a casing assembly conduit 208 configured to cool thecooling fluid. The motor cooling conduit 206 defines a pathway forconveying a cooling fluid through or around at least a portion of theelectric motor, and has a thermally conductive relationship with the atleast a portion of the electric motor 102. The motor cooling conduit 206may have any desired configuration, including a cooling jacketsurrounding at least a portion of the electric motor, and/or one or moreinternal channels, tubes, pathways, inter-connected or interlaced unitcells, or the like within or surrounding the rotor and/or stator of theelectric motor.

The casing assembly conduit 208 is integrally formed within at least aportion of the casing assembly 118. For example, the casing assemblyconduit 208 may include a plurality of internal channels, tubes,pathways, inter-connected or interlaced unit cells, or the likeintegrally formed within at least a portion of the casing assembly 118.The casing assembly conduit 208 defines a pathway for conveying acooling fluid through at least a portion of the casing assembly 118, andhas a thermally conductive relationship with an external surface of thecasing assembly 118, such as an external surface of the motor casing120, an external surface of the inner surface 128 of the nacelle 122, anexternal surface of the outer surface 126 of the nacelle 122, and/or anexternal surface of one or more of the support members (e.g., fan outletguide vanes) 124. Cooling fluid flowing out of the casing assemblyconduit 208 may flow into a fluid reservoir 210, such as an expansiontank or the like.

The pump 202 is operably coupled to the drive shaft 110. The electricmotor 102 rotates the driveshaft 110, and the driveshaft operates thepump 202, causing the pump 202 to circulate cooling fluid through thefluid pathway 204. The pump 202 may be operably coupled to thedriveshaft 110 either directly or across a gearbox, as desired, toobtain a desired pump speed relative to the rotational speed of thedriveshaft.

During operation, the pump 202 circulates cooling fluid through themotor cooling conduit 206, thereby transferring heat from the electricmotor 102 to the cooling fluid. The cooling fluid exits the motorcooling conduit 206, having been heated by the thermally conductiverelationship with the electric motor 102. The cooling fluid thencirculates through the casing assembly conduit 208 integrally formedwithin the casing assembly 118. Airflow passes over the external surfaceof the casing assembly 118, and heat transfers from the cooling fluid tothe airflow. The cooling fluid exits the casing assembly conduit 208,having been cooled by the thermally conductive relationship with theexternal surface of the casing assembly 118. The cooling fluid thencirculates back to the pump 202, and again through the motor coolingconduit 206.

In some embodiments, a fan or propeller 112 operably coupled to thedrive shaft 110 forces airflow 132 over the external surface of thecasing assembly 118 and/or over the surface of the electric motor 102.Cooling fluid passing through the casing assembly conduit 208 is cooledby airflow passing over the surface of the casing assembly 118, withinwhich the casing assembly conduit 208 are integrally formed.

The casing assembly may have any desired configuration. As shown in FIG.2A, the casing assembly 118 may include a motor casing 120. As shown inFIGS. 2B and 2C, the casing assembly 118 may include a fan casing ornacelle 122 and a plurality of circumferentially spaced support members(e.g., fan outlet guide vanes) 124 that circumferentially support thefan casing or nacelle 122 about the motor casing 120. The casingassembly conduit may be integrally formed within the motor casing 120(FIG. 2A), within the nacelle 122 and/or one or more of the supportmembers 124 (FIG. 2B), and/or within both the motor casing 120, and thenacelle 122 and/or support members 124 (FIG. 2C). Additionally, or inthe alternative, in the embodiment shown in FIG. 2A, the motor casing120 may serve as a nacelle defining an external surface of the electricpropulsion assembly. Where the motor casing functions as a nacelle, insome embodiments, the motor casing 120 may circumferentially surround atleast a portion of the fan section 104.

Referring now to FIGS. 3A-3C, in another exemplary embodiment, anintegrated cooling system 300 provides two-phase cooling. The integratedcooling system 300 shown in the embodiments of FIGS. 3A-3C may operateas a refrigeration cycle or a heat pump. As shown in FIGS. 3A-3C, anelectric motor with an integrated cooling system 300 may include acompressor 302 and an expansion valve 304 operably configured to effecta cyclical phase change from vapor that condenses in a casing assemblyconduit 306 to liquid that evaporates in a motor cooling conduit 308.

The compressor 302 is operably coupled to the drive shaft 110. Theelectric motor 102 rotates the driveshaft 110, and the driveshaft 110operates the compressor 302, causing the compressor 302 to circulatecooling fluid through the fluid pathway 310. The compressor 302 may beoperably coupled to the driveshaft 110 either directly or across agearbox, as desired, to obtain a desired compressor speed relative tothe rotational speed of the driveshaft. The expansion valve 304 may beprovided in fluid communication with an aspect of the fluid pathway 310located between the casing assembly conduit 306 and the motor coolingconduit 308. the expansion valve imparts a liquid-to-vapor phase changeto at least a portion of the cooling fluid flowing from the casingassembly conduit 306.

The casing assembly conduit 306 defines a pathway for conveying acooling fluid through at least a portion of the casing assembly 118, andhas a thermally conductive relationship with an external surface of thecasing assembly 118, such as an external surface of the motor casing120, an external surface of the inner surface 128 of the nacelle 122, anexternal surface of the outer surface 126 of the nacelle 122, and/or anexternal surface of one or more of the support members (e.g., fan outletguide vanes) 124. The motor cooling conduit 308 defines a pathway forconveying a cooling fluid through or around at least a portion of theelectric motor, and has a thermally conductive relationship with the atleast a portion of the electric motor 102.

During operation, cooling fluid circulates through a fluid pathway 310.The cooling fluid enters the compressor 302 as vapor or saturated vapor,having been heated or superheated when passing through the motor coolingconduit 308 by heat transferring from the electric motor 102 to thecooling fluid. An accumulator 312 may be located upstream of thecompressor 302, for example, to prevent liquid from entering thecompressor 302. The vapor or superheated vapor exits the compressor 302and flows through the fluid pathway 310, entering the casing assemblyconduit 306 integrally formed within at least a portion of the casingassembly 118. Airflow passes over the external surface of the casingassembly 118, within which the casing assembly conduit is integrallyformed. The vapor or superheated vapor is cooled and condenses at itpasses through the casing assembly conduit 306. The cooling fluid exitsthe casing assembly conduit 306 as saturated liquid, having been cooledby the thermally conductive relationship with the external surface ofthe casing assembly 118. The cooling fluid then passes through theexpansion valve 304, where the cooling fluid undergoes an abruptreduction in pressure, causing adiabatic flash evaporation of at least aportion of the cooling fluid. The flash evaporation of the cooling fluidlowers the temperature of the cooling fluid, which then enters the motorcooling conduit 308, cooling the electric motor 102 by the thermallyconductive relationship between the motor cooling conduit and at least aportion of the electric motor 102.

In some embodiments, a fan or propeller 112 operably coupled to thedrive shaft 110 forces airflow 132 over the external surface of thecasing assembly 118 and/or over the surface of the electric motor 102.As shown in FIG. 3A, the casing assembly 118 may include a motor casing120, and as shown in FIGS. 3B and 3C, the casing assembly 118 mayinclude a fan casing or nacelle 122 and a plurality of circumferentiallyspaced support members (e.g., fan outlet guide vanes) 124 thatcircumferentially support the fan casing or nacelle 122 about the motorcasing 120. The casing assembly conduit may be integrally formed withinthe motor casing 120 (FIG. 3A), within the nacelle and/or the supportmembers 124 (FIG. 3B), and/or within both the motor casing 120 and thenacelle and/or support members 124 (FIG. 3C). Additionally, or in thealternative, in the embodiment shown in FIG. 3A, the motor casing 120may serve as a nacelle defining an external surface of the electricpropulsion assembly. Where the motor casing functions as a nacelle, insome embodiments, the motor casing 120 may circumferentially surround atleast a portion of the fan section 104.

Referring now to FIGS. 4A and 4B, aspects of an exemplary casingassembly will be described in more detail. As discussed herein, a casingassembly may include a motor casing 120 and/or a fan casing or nacelle122 (FIG. 4A), and a plurality of circumferentially spaced supportmembers 124 such as fan outlet guide vanes 125 and/or struts 127 (FIG.4B) that circumferentially support the fan casing or nacelle 122 aboutthe motor casing 120. In some embodiments, the casing assembly 118 mayinclude one or more annular casings 400 such as depicted in FIG. 4A andone or more support members 402 as depicted in FIG. 4B. The annularcasing 400 depicted in FIG. 4A may be a motor casing 120 and/or a fancasing or nacelle 122. In some embodiments, a plurality of annularcasings 400 may be provided, such as a motor casing 120 thatcircumferentially surrounds at least a portion of the fan 112, theelectric motor 102, and/or the core turbine engine, together with a fancasing or nacelle 122 that circumferentially surrounds at least aportion of the motor casing 120, the fan 112, the electric motor 102,and/or the core turbine engine. The support member 402 depicted in FIG.4B may be a fan outlet guide vane 125 or a strut 127. A plurality ofthese support members 402 may be provided, for example, together withone or more annular casings 400. For example, one or more supportmembers 402 may be provided to circumferentially support the fan casingor nacelle 122 about the motor casing 120, and/or to circumferentiallysupport the motor casing 120 about the electric motor 102 and/or coreturbine engine.

At least a portion of the casing assembly includes a casing assemblyconduit 404 integrally formed therein. The casing assembly conduit 404may include any desired configuration. In some embodiments, the casingassembly conduit 404 may include an array of internal channels, tubes,pathways, or the like. The casing assembly conduit 404 may have a linearconfiguration and/or a more complex configuration, such as a serpentine,racetrack, or fishbone configuration. In some embodiments, the casingassembly conduit 404 may include an array of inter-connected orinterlaced unit cells. In some embodiments, such unit cells may providestructural support in addition to providing a casing assembly conduit404.

Various aspects of the casing assembly 118 or the casing assemblyconduit 208 and/or various aspects of the motor cooling conduit 206 maybe manufactured using any desired technology, including machining,drilling, casting, additive manufacturing, a combination thereof, or anyother technique. An additive manufacturing process may include anyprocess which involves layer-by-layer construction or additivefabrication (as opposed to material removal as with conventionalmachining processes). Such processes may also be referred to as “rapidmanufacturing processes”. Additive manufacturing processes include, butare not limited to: Direct Metal Laser Melting (DMLM), Laser Net ShapeManufacturing (LNSM), electron beam sintering, Selective Laser Sintering(SLS), 3D printing, such as by inkjets and laserjets, Binder Jetting(BJ), Material Jetting (MJ), Photopolymer Jetting (PJ), Sterolithography(SLA), Electron Beam Melting (EBM), Fused Deposition Modeling (FDM),Laser Engineered Net Shaping (LENS), Direct Metal Deposition (DMD), andHybrid Processes (HP).

Any desired materials may be used to manufacture the componentsdescribed herein. Exemplary materials include aluminum alloys, steelalloys, titanium alloys, nickel alloys (e.g., superalloys), andcomposites such as ceramic matrix composite (CMC) materials. ExemplaryCMC materials may include silicon carbide, silicon, silica, or aluminamatrix materials and combinations thereof. Ceramic fibers may beembedded within the matrix, such as oxidation stable reinforcing fibersincluding monofilaments like sapphire and silicon carbide, yarnincluding silicon carbide, alumina silicates, and chopped whiskers andfibers, and optionally ceramic particles (e.g., oxides of Si, Al, Zr, Y,and combinations thereof) and inorganic fillers (e.g., pyrophyllite,wollastonite, mica, talc, kyanite, and montmorillonite). As furtherexamples, the CMC materials may also include silicon carbide (SiC) orcarbon fiber cloth.

The present disclosure additionally embraces methods of cooling anelectric motor, which, for example, may include an electric motoremployed in an electric propulsion system for an aircraft. FIG. 5 showsan exemplary method 500 of cooling an electric motor used for propulsionof an aircraft. The exemplary method 500 includes circulating a coolingfluid through a motor cooling conduit 502. The motor cooling conduitdefines a pathway for conveying a cooling fluid through or around atleast a portion of the electric motor, and has a thermally conductiverelationship with at least a portion of an electric motor, such as astator and/or a rotor of the electric motor. As such, the method 500provides for transferring heat from the electric motor to the coolingfluid circulating through the motor cooling conduit 504. Next, themethod 500 proceeds with circulating the cooling fluid through a casingassembly conduit integrally formed within at least a portion of a casingassembly that circumferentially surrounds at least a portion of theelectric motor 506. The casing assembly conduit defines a pathway forconveying the cooling fluid through the at least a portion of the casingassembly, and has a thermally conductive relationship with an externalsurface of the casing assembly. As such, the method 500 provides fortransferring heat from the cooling fluid circulating through the casingassembly conduit to airflow passing over the external surface of thecasing assembly 508.

In the exemplary method 500, the cooling fluid is circulated through themotor cooling conduit 206 and the casing assembly conduit 208 at leastin part by a pump or a compressor that is operably coupled to the driveshaft 110 of the electric motor 102. In some embodiments, the method 500further includes accelerating a stream of airflow passing over theexternal surface of the casing assembly at least in part by a fan or apropeller 112, which may be operably coupled to the driveshaft 110.

Additionally, in the exemplary method, the casing assembly may include amotor casing 120, a fan casing or nacelle 122; and/or a plurality ofsupport members (e.g., fan outlet guide vanes) 124. The support members124 may circumferentially support the fan casing or nacelle 122 aboutthe motor casing 120, and/or the motor casing 120 about the electricmotor 102 and/or core turbine engine. In various embodiments of theexemplary method 500, at least a portion of the casing assembly conduit208 is integrally formed within at least a portion of the casingassembly 118 (e.g., at least a portion of the motor casing 120, at leasta portion of the nacelle 122, and/or at least a portion of one or moreof the plurality of support members 124).

While in general the presently disclosed integrated cooling systems aredescribed as closed systems (i.e. a pressurized system), such closedsystems are described by way of example and should not be interpreted aslimiting the present disclosure. It will be apparent to those skilled inthe art that such a closed system may include cooling fluid refilllines, cooling fluid reservoirs, cooling fluid bypass valves, coolingfluid bypass lines, among other things, any of which may be includedalone or in combination without departing from the spirit and scope ofthe present disclosure. Additionally, the presently disclosed integratedcooling systems need not be implemented in a closed system at all, butrather, in another exemplary embodiment the presently disclosedintegrated cooling systems may be implemented in an open system (i.e., anon-pressurized system).

This written description uses exemplary embodiments to describe thepresently disclosed subject matter, including the best mode, and also toenable any person skilled in the art to practice such subject matter,including making and using any devices or systems and performing anyincorporated methods. As used herein, the terms “first”, “second”, and“third” may be used interchangeably to distinguish one component fromanother and are not intended to signify location or importance of theindividual components. It is also understood that terms such as “top”,“bottom”, “outward”, “inward”, and the like are words of convenience andare not to be construed as limiting terms. The terms “a” and “an” do notdenote a limitation of quantity, but rather denote the presence of atleast one of the referenced item.

The patentable scope of the presently disclosed subject matter isdefined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they include structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

What is claimed is:
 1. An electric machine having an integrated coolingsystem, the electric machine comprising: an electric motor comprising astator, a rotor, and a drive shaft operably coupled to the rotor; amotor cooling conduit that defines a pathway for conveying a coolingfluid through or around at least a portion of the electric motor, themotor cooling conduit having a thermally conductive relationship withthe at least a portion of the electric motor; a casing assembly thatcircumferentially surrounds at least a portion of the electric motor,the casing assembly comprising: an annular casing; a plurality ofsupport members extending radially from the annular casing andcircumferentially spaced relative to the annular casing; and a casingassembly conduit integrally formed within at least a portion of thecasing assembly wherein the casing assembly conduit and the at least aportion of the casing assembly define a monolithic, single-piececonstruction, the casing assembly conduit defining a pathway forconveying the cooling fluid through the at least a portion of the casingassembly, the casing assembly circumferentially surrounding at least aportion of the electric motor, and the casing assembly conduit having athermally conductive relationship with an external surface of the casingassembly; and a pump or compressor operably coupled to the drive shaft,the pump or compressor being operably configured to circulate thecooling fluid through the motor cooling conduit and the casing assemblyconduit.
 2. The electric machine of claim 1, wherein at least a portionof the casing assembly conduit is integrally formed within one or moreof the plurality of support members.
 3. The electric machine of claim 1,wherein at least a portion of the casing assembly conduit being isintegrally formed within at least a portion of the annular casing. 4.The electric machine of claim 1, wherein the casing assembly comprises anacelle, with at least a portion of the casing assembly conduit beingintegrally formed within at least a portion of the nacelle.
 5. Theelectric machine of claim 1, wherein the plurality of support memberscomprise fan outlet guide vanes and/or struts.
 6. The electric machineof claim 1, wherein the annular casing is configured as a motor casing,the casing assembly further comprising a nacelle, and the plurality ofsupport members configured as a plurality of fan outlet guide vanescircumferentially supporting the nacelle about the motor casing, with atleast a portion of the casing assembly conduit being integrally formedwithin at least a portion of the motor casing, at least a portion of thenacelle, and/or at least a portion of one or more of the plurality offan outlet guide vanes.
 7. The electric machine of claim 1, whereinduring operation, cooling fluid circulates through the motor coolingconduit, thereby transferring heat from the electric motor to thecooling fluid by the thermally conductive relationship with the at leasta portion of the electric motor.
 8. The electric machine of claim 1,wherein during operation, heat transfers from the electric motor to thecooling fluid by evaporation of at least a portion of the cooling fluidcirculating through the motor cooling conduit, at least a portion of thecooling fluid entering the motor cooling conduit as a liquid.
 9. Theelectric machine of claim 1, comprising a fan or a propeller operablycoupled to the drive shaft.
 10. The electric machine of claim 1, whereinduring operation, airflow passes over the external surface of the casingassembly, thereby transferring heat to the airflow from the coolingfluid circulating through the casing assembly conduit by the thermallyconductive relationship with the external surface of the casingassembly.
 11. The electric machine of claim 1, wherein during operation,heat transfers from the cooling fluid to airflow passing over theexternal surface of the casing assembly by condensation of at least aportion of the cooling fluid circulating through the casing assemblyconduit, at least a portion of the cooling fluid entering the casingassembly conduit as a vapor.
 12. The electric machine of claim 1,further comprising an expansion valve in fluid communication with anaspect of the pathway located between the casing assembly conduit andthe motor cooling conduit, the expansion valve configured to impart aliquid-to-vapor phase change to at least a portion of the cooling fluidflowing from the casing assembly conduit.
 13. An electric propulsionsystem for an aircraft, the system comprising: an electric motorcomprising a stator, a rotor, and a drive shaft operably coupled to therotor; a motor cooling conduit that defines a pathway for conveying acooling fluid through or around at least a portion of the electricmotor, the motor cooling conduit having a thermally conductiverelationship with the at least a portion of the electric motor; a casingassembly that circumferentially surrounds at least a portion of theelectric motor, the casing assembly comprising: a motor casing; anacelle; and a casing assembly conduit integrally formed within at leasta portion of the casing assembly wherein the casing assembly conduit andthe at least a portion of the casing assembly define a monolithic,single-piece construction, the casing assembly conduit defining apathway for conveying the cooling fluid through the at least a portionof the casing assembly, and the casing assembly conduit having athermally conductive relationship with an external surface of the casingassembly; and a pump or compressor operably coupled to the drive shaft,the pump or compressor being operably configured to circulate coolingfluid through the motor cooling conduit and the casing assembly conduit,wherein, during operation, airflow passes over the external surface ofthe casing assembly, thereby transferring heat to the airflow from thecooling fluid circulating through the casing assembly conduit by thethermally conductive relationship with the external surface of thecasing assembly.
 14. The electric propulsion system of claim 13, whereinthe casing assembly conduit further comprises a plurality of supportmembers circumferentially supporting the nacelle about the motor casing.15. The electric propulsion system of claim 14, comprising least aportion of the casing assembly conduit being integrally formed within atleast a portion of the motor casing, at least a portion of the nacelle,and/or at least a portion of one or more of the plurality of supportmembers.
 16. The electric propulsion system of claim 13, furthercomprising a fan or a propeller operably coupled to the drive shaft. 17.A method of cooling an electric machine used for propulsion of anaircraft, the method comprising: circulating a cooling fluid through amotor cooling conduit that defines a pathway for conveying a coolingfluid through or around at least a portion of an electric motor, themotor cooling conduit having a thermally conductive relationship withthe at least a portion of an electric motor, the electric motorcomprising a stator and a rotor; transferring heat from the electricmotor to the cooling fluid circulating through the motor cooling conduitby the thermally conductive relationship with the at least a portion ofthe electric motor; and circulating the cooling fluid through a casingassembly conduit integrally formed within at least a portion of a casingassembly wherein the casing assembly conduit and the at least a portionof the casing assembly define a monolithic, single-piece construction,the casing assembly comprising a motor casing, a nacelle, and aplurality of support members circumferentially supporting the nacelleabout the motor casing, the casing assembly conduit defining a pathwayfor conveying the cooling fluid through the at least a portion of thecasing assembly, the casing assembly circumferentially surrounding atleast a portion of the electric motor, and the casing assembly conduithaving a thermally conductive relationship with an external surface ofthe casing assembly, wherein the cooling fluid is circulated through themotor cooling conduit and the casing assembly conduit at least in partby a pump or a compressor operably coupled to a drive shaft, the driveshaft operably coupled to the rotor of the electric motor.
 18. Themethod of claim 17, further comprising accelerating an airflow passingover the external surface of the casing assembly at least in part by afan or a propeller operably coupled to a driveshaft.
 19. The method ofclaim 17, wherein at least a portion of the casing assembly conduitbeing integrally formed within at least a portion of the motor casing,at least a portion of the nacelle, and/or at least a portion of one ormore of the plurality of support members.
 20. The method of claim 17,comprising: transferring heat from the electric motor to the coolingfluid by evaporation of at least a portion of the cooling fluidcirculating through the motor cooling conduit, at least a portion of thecooling fluid entering the motor cooling conduit as a liquid; and/ortransferring heat from the cooling fluid to an airflow passing over theexternal surface of the casing assembly by condensation of at least aportion of the cooling fluid circulating through the casing assemblyconduit, at least a portion of the cooling fluid entering the casingassembly conduit as a vapor.